Patents Assigned to VTech Communication, Ltd.
  • Patent number: 5502420
    Abstract: A voltage controlled oscillator apparatus for generating a desired frequency, set by a tuning voltage, toward modulating a transmission signal on the desired frequency. The voltage controlled oscillator apparatus includes an oscillator transistor the base of which is RF live so as to destabilize the transistor such that it oscillates. The oscillator transistor emitter is operably connected through a capacitor to a tank circuit, which stores RF energy at the desired frequency, based on the tuning voltage, to set the oscillator transistor frequency. The inherent collector-base junction capacitance serves to provide voltage variable capacitance resulting in the generation of a carrier signal. The oscillator transistor collector is electrically connected to an amplifier transistor's emitter, such that the amplified transistor and oscillator transistor are in cascode configuration. The amplifier transistor amplifies the transmission signal input at its base and presents a signal output on its collector.
    Type: Grant
    Filed: June 1, 1994
    Date of Patent: March 26, 1996
    Assignee: VTech Communications, Ltd.
    Inventor: Michael J. Barclay
  • Patent number: 5497125
    Abstract: A power control system for controlling the power output of a power amplifier. The power control system draws power from a variable voltage supply, such as a battery, and receives a signal input which indicates the desired power output. The power control system includes a power amplifier for amplifying an electrical signal which draws a current from the variable voltage supply. The power amplifier is of the type wherein the operating current drawn by the power amplifier is indicative of the power output. The power control system additionally includes a current sense circuit, which is operably connected between the variable voltage supply and the power amplifier and which senses the current drawn by the power amplifier and simultaneously produces an output current, which is directly correlated to the sensed current. The output current and the signal input are compared in a controller which produces a control signal for controlling the power output by the power amplifier.
    Type: Grant
    Filed: June 1, 1994
    Date of Patent: March 5, 1996
    Assignee: Vtech Communications, Ltd.
    Inventor: Ian D. Royds